1. Field of the Invention
The present invention relates to capacitor elements, manufacturing methods therefor, and substrates for semiconductor devices having capacitor elements.
2. Description of the Related Art
Recently, in semiconductor devices, operating frequencies of semiconductor elements thereof are becoming higher. Based on this, it is becoming necessary to stabilize power supply voltages supplied to the semiconductor elements. In order to deal with this necessity, a structure has been proposed in which a capacitor element is provided in a substrate (semiconductor device substrate) for a semiconductor device on which substrate a semiconductor element is mounted.
FIG. 1 shows a conventional semiconductor device 10. The semiconductor device 10 has a structure in which a semiconductor element 12 is mounted on a semiconductor device substrate 11. The substrate 11 has a structure in which a capacitor element 14 is provided inside a substrate body 13. The capacitor element 14 has a structure in which a film 16 made of a dielectric material is formed on a top surface of a silicon substrate 15, and a conductive film 17 is formed on the film 16 (refer to Japanese Laid-Open Patent Application No. 2001-274034, for example).
The capacitor element 14 has the structure in which the silicon substrate 15 serves as the base. Hence, when forming a through-hole in the silicon substrate 15, it is necessary to perform dry etching, wet etching, or laser processing, for example, which results in a further process in manufacturing. In addition, since the silicon substrate 15 is a semiconductor, it is necessary to form an insulating film on the inside surface of the through-hole and the top surface of the silicon substrate 15 before filling the through-hole with Cu, for example, so as to secure insulation. This also results in a further process in manufacturing.
When the thickness of a silicon substrate is reduced, the strength is decreased and cracking tends to occur. Hence, it is difficult to reduce the thickness. Here, the base is the silicon substrate 15. Thus, the thickness of the capacitor element 14 cannot be reduced, and the thickness of the substrate 11 is increased for that amount.
The capacitor element 14 is arranged at a position distant from a semiconductor element mounting surface of the substrate 11. Thus, the conductive channel between the semiconductor element 12 and the capacitor element 14 is long, and the inductance thereof is high. Hence, in a case where the operating frequency of the semiconductor element 12 becomes higher, there is the possibility that stabilization of power supply voltage supplied to the semiconductor element 12 becomes difficult due to the inductance.